Interstitial lactate levels in human skin at rest and during an oral glucose load: a microdialysis study

In vitro data have suggested that the skin is a significant lactate source. The purpose of the present study was to measure lactate and glucose concentrations in intact human skin in vivo using the microdialysis technique. Microdialysis fibres of 216 microns were inserted intradermally and perfused at a rate of 3 microliters min-1. In the first experimental protocol, dialysis fibres were calibrated by the method of no net flux in eight subjects. Skin lactate concentrations of 2.48 +/- 0.17 mmol l-1 were significantly greater than lactate concentrations of 0.84 +/- 0.15 mmol l-1 in venous plasma (P < 0.01). Glucose concentrations in skin and venous plasma were similar (5.49 +/- 0.18 vs. 5.26 +/- 0.24 mmol l-1). In the second experimental protocol, changes in lactate and glucose levels were studied in 10 subjects after an oral glucose tolerance test (OGTT). After the OGTT, plasma glucose and lactate levels increased by 54% and 39% to peak levels at 30 and 60 min respectively. In comparison, skin glucose and lactate increased by 41% and 18% at 60 and 90 min. No changes in skin blood flow were observed during the OGTT. The data suggest that resting skin is a significant lactate source with no significant lactate production during OGTT. The cellular source of lactate in the skin remains undetermined to date.